The hardening of steel by heating it to a temperature at which the steel is in an austenitic state and then cooling it by a quenching operation is well known in the art. When hardening flat objects, such as flat discs, gears, wheels, etc. by ordinary methods, it is difficult to avoid warpage of the articles because of uneven immersion of the article or uneven spraying by a quenching liquid. Also, as the article must be supported during a spray quenching, substantial areas of the article are covered by the support means and thus are not exposed to the quenching spray; resulting in uneven cooling which leads to undesirable deformation of the article.
Present methods of quenching discs, such as agricultural discs, rely on quenching in oil or Austempering in a salt bath, and water spray quenching has not been applied to these discs or similar parts. The present invention, however, utilizes an effective water spray quench for the heated articles to provide a substantially uniform and rapid cooling of the article from an austenitic to a martensitic state.
The present invention comprehends a process for water spray quenching of agricultural discs and similar articles where the disc is received from a furnace at an appropriate temperature and is quenched by a controlled pressure water spray delivered simultaneously to both sides of the article, with the spray being of uniform intensity across the entire area of the article. The article remains stationary during the quenching operation and is supported during quenching upon a series of support pins which are of such dimensions as to reduce to a minimum the blockage of the spray on the article to be quenched.
The present invention provides a water spray quenching for a steel article to achieve the desired transformation from the austenitic to the martensitic stage. In conventional oil quench processes, high carbon steels are required in order to achieve the desired transformation during quenching. The more severe water spray quench of the present process enables the use of lower carbon and/or lower alloy steel resulting in a product which has a superior impact strength. Also, a steel having a lower hardenability may be used with the water spray quench to achieve the desired results.
The present invention further comprehends a quenching operation using a water spray which will provide lower initial costs and lower replacement costs for the quenchant as compared to an oil quench system. The replacement of the oil quench with a water quench will also eliminate the fire hazards associated with oil and any pollution control problems due to an oil quench.
The unique process described above may be summarized as a process for hardening steel articles by water quenching comprising the steps of heating the article to a temperature above its austenitizing temperature, rapidly moving the article to a quenching zone and retaining the article in a stationary position, simultaneously spraying both sides of the article with water to effectively and completely transform the article to martensite, and expelling the quenched article from the quenching zone.
A further consideration for the present invention is the provision of a novel water spray quenching apparatus for handling and cooling the hot article from the austenitizing furnace. A conveyor leads from the furnace into the quenching station where the heated article is suitably positioned relative to the spray quenching nozzles. The conveyor within the quenching station then drops away to leave the article supported on a series of support pins and water is simultaneously sprayed onto both the upper and lower surfaces of the horizontally oriented article. Once the spray is terminated, the conveyor is moved upward to engage the cooled article and expell it from the quenching station.
Further objects are to provide a method and apparatus of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.